Master of Science / Department of Mechanical and Nuclear Engineering / Liang-Wu Cai / The study on artificially created materials has much evidence of naval properties. Phononic Crystals (PCs) are new class of artificially constructed materials. They have a large number of scattering inclusions that are embedded in a homogeneous host material. These scatterers are arranged in periodic lattice structures. The scatterers and host materials are usually either solids or fluids. Phononic materials are useful due to their ability to hinder the existence of certain frequencies over which the propagation of elastic and acoustic waves are forbidden. The formation of phononic band gaps (PBGs) in PCs is determined by the material properties and the geometry of the periodic lattice structures. Some PCs have full band gaps [14, 55] while others have partial band gaps [35]. Although the study of PCs is an attractive area for many researchers, the investigations on PCs are just emerging. The aim of the thesis is to study on perform fabrication and experimental characterization of 2-D PCs having eccentrically layered scatterers. In addition, the influence of the eccentricity of the layered scatterers on the amplitude spectrums are experimentally observed. Hence, the main objective in this work is to characterize the influence of the eccentricity orientation angles on the transmitted amplitude spectra. The layered scatterers were created by inserting the paraffin-coated stainless steel rods into the cavities. Two sets of stainless steel rod diameters (2 mm and 2.5 mm) were used. The eccentricity orientation angles of scatterers were changed from 0 degree to 90 degrees at the increment of 22.5 degrees. Ultrasonic waves were introduced into the test pieces to observe the propagated waves through the material. The ultrasonic Through Transmission Test (TTT) followed by signal processing techniques was employed to produce the transmitted spectra of PCs. The frequency dependent amplitude spectrums were observed at the chosen frequency ranges with the help of MATLAB and Fast Fourier Transformation (FFT) function. The results show that the geometry and the material parameters change the attenuation of amplitudes by hindering the wave propagation. This leads PC as a good candidate for a sound barrier for controlling the wave propagation or vibrations within the chosen frequency ranges. Keywords: Phononic Crystal/s (PC or PCs); Phononic Band Gap/s (PBG or PBGs); Through Transmission Test (TTT), Fast Fourier Transformation (FFT), Square array, Triangular array, Amplitude spectrum/ Spectra, Eccentrically layered scatterers

Biology is a good source of analogies for engineering design. One approach of retrieving biological analogies is to perform keyword searches on natural-language sources such as books, journals, etc. A challenge in retrieving information from natural-language sources is the potential requirement to process a large number of search results. This thesis describes two methods on improving the relevancy of the search results. The first method is inserting metadata such as part- of-speech, word sense and lexicographical data for each word in a natural-language. The second method is categorizing the search results, using WordNet relationships and Wikipedia structures as ontologies. Although this research is still exploratory, initial qualitative observations demonstrate successful identification and separation of biological phenomena relevant to either desired functions or desired qualities. The benefits of embedding metadata are demonstrated through a case study on the redesign of a fuel cell bipolar plate. A prototype was constructed with ability to passively prevent prolonged catastrophic flooding.

Biology is a good source of analogies for engineering design. One approach of retrieving biological analogies is to perform keyword searches on natural-language sources such as books, journals, etc. A challenge in retrieving information from natural-language sources is the potential requirement to process a large number of search results. This thesis describes two methods on improving the relevancy of the search results. The first method is inserting metadata such as part- of-speech, word sense and lexicographical data for each word in a natural-language. The second method is categorizing the search results, using WordNet relationships and Wikipedia structures as ontologies. Although this research is still exploratory, initial qualitative observations demonstrate successful identification and separation of biological phenomena relevant to either desired functions or desired qualities. The benefits of embedding metadata are demonstrated through a case study on the redesign of a fuel cell bipolar plate. A prototype was constructed with ability to passively prevent prolonged catastrophic flooding.

A mathematically consistent algorithm for simulating interfacial turbulent flows is devised in this work. To minimize numerical errors for imposing dynamic boundary conditions at the interface locations, piezometric pressure is used to limit the effect of gravity forces in a flow field. Consequently, suitable and consistent numerical schemes are designed to accurately implement the new forms of interfacial forces. The proposed numerical methods are challenged for low Froude number flows which tend to trouble conventional algorithms. To capture the effect of turbulence on the interface, standard large eddy simulation techniques are reviewed and discussed. It is shown the standard filtered flow equations encounter numerical and mathematical inconsistencies. To remedy the irregularities of the conventional methods, a new framework for large eddy simulations is grounded. Purely mathematical models are derived and correlated with the conventionally more physical models. Semi implicit SIMPLE method is used to discretize the final flow equations. Taking advantage of the implicit feature of SIMPLE algorithm, an error correction technique is devised by which numerical cost of a turbulent simulation is substantially reduced. The entire framework is finally discussed toward simulating a turbulent interfacial flow.

A pneumatic droplet generator is described, which consists of a T-junction with a nozzle fit into one opening, the second opening is connected to a gas cylinder through a solenoid valve and the third connected to a length of steel tubing. The droplet generator is filled with liquid. Opening the valve for a preset time creates a pulse of alternating negative and positive pressure in the gas above the surface of the liquid. A jet of liquid issues far enough out of the nozzle that its tip becomes unstable, detaches and forms a droplet. Experiments were conducted using water/glycerin mixtures and molten metals including tin, zinc and zinc alloy. Droplet formation was photographed and the pressure variation inside the droplet generator recorded. The effect of various experimental parameters such as nozzle size, pressure pulse width, secondary gas flow pressure, liquid viscosity and temperature on droplet formation were investigated. An analytic model of incompressible liquid motion in the nozzle is used to explain the behavior of water/glycerin solutions inside the nozzle and droplet formation. The model demonstrates that the motion of the surface is out of phase with the exciting pressure oscillation. Experiments showed the oscillation of the liquid surface prior to droplet ejection and the time lag between the pressure oscillation and droplet ejection. The model predicts that maximum liquid velocity is attained at an intermediate value of viscosity, and experiments confirmed that the largest liquid motion was achieved with this intermediate value, which eventually leads to droplet formation. Similarly, with molten metals, a simple analytical method was used to estimate the diameter of droplets. The size of tin droplets measured from experiments was in good agreement with that obtained from the model.

The physical mechanism responsible for droplet manipulation in electrowetting on dielectric (EWOD) devices is not yet fully understood. This investigation will examine the role of capillary forces on droplet manipulation to further the physical understanding of these devices. An analytical model for the capillary force acting on a confined droplet at equilibrium is developed here. Model predictions were validated using optical measurements of the droplet interface in the vertical plane. It was found that the capillary force and interface shape predicted by the equilibrium model were over an order of magnitude more accurate than predictions from the model commonly used in EWOD investigations. The equilibrium model was adapted to droplets with arbitrary shapes to predict droplet dynamics in EWOD devices. It was found that droplet motion could be described using the driving capillary force and frictional forces from wall shear, the contact line, and contact angle hysteresis. Comparison with experimental data shows that this model accurately predicts the effects of applied voltage and droplet aspect ratio on the transient position and velocity of droplets. This model can be used to design EWOD devices and predict the simultaneous manipulation of droplets required to meet the high throughput demands of practical applications. A robust system for droplet monitoring must be automated before EWOD devices can be used reliably in practical applications. Although capacitance measurements have been used to automate droplet detection in EWOD devices, manual optical measurements are generally used to monitor droplet mixing. This may not be possible in high throughput applications with multiple droplets and limited optical access. Here, capacitance measurements are shown to be an accurate and repeatable means of monitoring droplet composition and real time mixing. Experiments were performed with this technique to show that mixing efficiency is better characterized by the number of translations required for full mixing, not mixing time.

Phase change materials (PCM) such as paraffin wax are known to exhibit slow thermal response due to their relatively low thermal conductivity. In this study, experiments were carried out to investigate a method of enhancing thermal conductivity of paraffin wax by making use of high porosity open cell metal foams. By adding metal foam, thermal conductivity of PCM’s was shown to increase by 16-18 times that of pure paraffin wax. The use of open cell metal foam material for thermal energy storage application was also investigated by designing and testing different thermal energy storage systems (TESS) - with and without metal foam. The effect of copper metal foam on heat transfer during melting and solidification was analysed by determining the convective heat transfer coefficient. Lastly, a numerical code was developed to predict the temperature field within PCM while melting.

This thesis presents an experimental analysis of the effect of temperature and thermal cycles on the performance of PZT ceramics in fuel injector applications. Due to the increase in the implementation of piezoceramics in applications such as fuel injection technology, it is imperative to understand how temperature affects piezoceramic performance. In this project, the fundamental piezoelectric properties (d_33, ε_33^T, s_33^E) of bulk PZT samples and high electric-field properties of piezoelectric stack actuators were obtained with respect to temperature and thermal cycles. The results show that increasing temperature will increase the fundamental piezoelectric properties of bulk piezoceramics, capacitance of stack actuators, and the displacement of piezoactuators in the absence of external load. Raising the temperature while applying a constant preload will initially increase piezoactuator displacement, but decrease it at higher temperatures. Temperature had a negative effect on the hysteresis in the displacement-voltage. Additionally, thermal hysteresis decreased significantly in subsequent temperature cycles.

Robotic Nanomaterial Manipulation inside scanning electron microscopes (SEM) is useful for prototyping functional devices and characterizing one-dimensional nanomaterial’s properties. Conventionally, manipulation of nanowires has been performed via teleoperation, which is time-consuming and highly skill-dependent. Manual manipulation also has the limitation of low success rates and poor reproducibility. This research focuses on a robotic system capable of automated pick-place of single nanowires. Through SEM visual detection and vision-based motion control, the system transferred individual silicon nanowires from their growth substrate to a microelectromechanical systems (MEMS) device that characterized the nanowires’ electromechanical properties. The performances of the nanorobotic pick-up and placement procedures were quantified by experiments. The system demonstrated automated nanowire pick-up and placement with high reliability. A software system for a load-lock-compatible nanomanipulation system is also designed and developed in this research.

Phase change materials (PCM) such as paraffin wax are known to exhibit slow thermal response due to their relatively low thermal conductivity. In this study, experiments were carried out to investigate a method of enhancing thermal conductivity of paraffin wax by making use of high porosity open cell metal foams. By adding metal foam, thermal conductivity of PCM’s was shown to increase by 16-18 times that of pure paraffin wax. The use of open cell metal foam material for thermal energy storage application was also investigated by designing and testing different thermal energy storage systems (TESS) - with and without metal foam. The effect of copper metal foam on heat transfer during melting and solidification was analysed by determining the convective heat transfer coefficient. Lastly, a numerical code was developed to predict the temperature field within PCM while melting.